Mayor Gavin Newsom wants to achieve a full Wi-Fi coverage of the city.

Joining several other municipalities poised to do the same thing, the city recently invited nonprofits and private businesses to bid on the proposed project, which would offer Wi-Fi access over the town's entire 49 square miles, according to Newsom's office. San Francisco already offers a free wireless hot spot at Union Square, a newly redeveloped shopping area that is lined with hotels.

One of the major goals of the project, according to Newsom's office, is to serve the city's less affluent by providing free or inexpensive wireless service to low-income neighborhoods. To augment that part of the plan, Newsom's office said, Dell and a handful of other computer makers have already agreed to provide free computers to the city's poor.

Administrators in some large cities view wireless broadband technology as a feasible, low-cost alternative to broadband services provided by commercial carriers such as phone companies and cable companies.

Philadelphia is among the largest cities aggressively pursuing a large-scale urban Wi-Fi network, with plans in place to have the system working by the end of 2006. Cities such as San Francisco and Philadelphia say urban Wi-Fi networks can help them save millions of dollars in operational costs by providing broadband connectivity for public-safety and other local government agencies. They also say that the networks will help boost economic development by drawing more people to the city.

But there are significant challenges ahead. For one, the technology hasn't proven itself capable of covering significantly large, densely populated areas, although several smaller cities, such as Chaska, Minn., have deployed citywide Wi-Fi. Also, the nation's top telephone operators, which are also broadband providers, have launched vigorous campaigns to squelch municipal Wi-Fi plans, seeing them as a threat to their own businesses.